Browsing by Author "Jared, Graham"
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Item Open Access CAD interface and framework for curve optimisation applications(Cranfield University, 2004-09) Munaux, Olivier; Jared, GrahamComputer Aided Design is currently expanding its boundaries to include more design features in its processes. Design is identified as an iterative process converging to solutions satisfying a set of constraints. Its close relation with optimisation indicate that there is strong potential for the integration of optimisation and CAD. The problem addressed in this thesis lies in interfacing the geometric representation of design with other non-geometric aspects. The example of free-form curve modelling is taken to investigate such relationships. Assumptions are made that Optimisation is powered by Evolutionary Computing algorithms like Genetic Algorithms (GA). The geometric definition of curves is commonly supported by NURBS, whose construction constraints are defined locally at the data points. Here the NURBS formulation is used with GA in an attempt to provide complementary handles on the curves shape other than the usual data point coordinates and control points weights. Differential properties are used for optimising NURBS, Hermite interpolation allows for the definition of higher order constraints (tangent, normal, bi-normal) at data points. The assignment of parameter values at the data points, known as parameterisation also provides control of the curve’s shape. Curve optimisation is also performed at the geometric modelling level. Old mathematical theorems established by Frénet and further developed by other mathematicians provide means of defining a curve’s shape with it’s intrinsic equations. Such representation is possible by using Function Representation (F-rep) algebra available in the ACIS software. Frep allows more generic and exact means of interfacing with the curve’s geometry and new functionality for curve inspection and optimisation are proposed in this thesis. The integration of optimisation findings and CAD are documented in the definition of a framework. The framework architecture proposed reconstructs a new CAD environment from separate elements bolted together in a generic Application Programming Interface (API) named “Oli interface”. Functionality created to interface optimisation and CAD makes a requirement list of the work that both sides should undertake to achieve design optimisation in the CAD environment.Item Open Access Evolutionary computing techniques for handling variable interaction in engineering design optimisation(2001-11) Tiwari, Ashutosh; Roy, Rajkumar; Jared, GrahamThe ever-increasing market demands to produce better products, with reduced costs and lead times, has prompted the industry to look for rigorous ways of optimising its designs. However, the lack of flexibility and adequacy of existing optimisation techniques in dealing with the challenges of engineering design optimisation, has prevented the industry from using optimisation algorithms. The aim of this research is to explore the field of evolutionary computation for developing techniques that are capable of dealing with three features of engineering design optimisation problems: multiple objectives, constraints and variable interaction. An industry survey grounds the research within the industrial context. A literature survey of EC techniques for handling multiple objectives, constraints and variable interaction highlights a lack of techniques to handle variable interaction. This research, therefore, focuses on the development of techniques for handling variable interaction in the presence of multiple objectives and constraints. It attempts to fill this gap in research by formally defining and classifying variable interaction as inseparable function interaction and variable dependence. The research then proposes two new algorithms, GRGA and GAVD, that are respectively capable of handling these types of variable interaction. Since it is difficult to find a variety of real-life cases with required complexities, this research develops two test beds (RETB and RETB-II) that have the required features (multiple objectives, constraints and variable interaction), and enable controlled testing of optimisation algorithms. The performance of GRGA and GAVD is analysed and compared to the current state-of-the-art optimisation algorithm (NSGAII) using RETB, RETB-II and other ‘popular’ test problems. Finally, a set of real-life optimisation problems from literature are analysed from the point of variable interaction. The performance of GRGA and GAVD is finally validated using three appropriately chosen problems from this set. In this way, this research proposes a fully tested and validated methodology for dealing with engineering design optimisation problems with variable interaction.Item Open Access Improving design coordination in computer supported environments in SMEs : implementation of a tool for capturing and analysing collaboration between actors(Cranfield University, 2007-09) Pol, Guillaume; Jared, Graham; Merlo, ChristopheTo remain competitive in a context of multi-partner projects companies are increasingly concerned with the coordination of design projects. Information systems such as PLM or CSCW are implemented to support the coordination of product information flows. Project managers are nevertheless finding it increasingly difficult to manage projects effectively. The impact of collaboration aspects on the design process is especially difficult for them to evaluate. Indeed, failing to integrate collaboration aspects into coordination can account for a great deal of design mistakes and finding a solution could lead to improved design coordination. The main obj ective of this researchi s then to help project managersi mprove coordination in design processes through a detailed analysis of collaboration between actors. A model of coordination and an associated model of collaboration have been devised together with a tool ("CoCa") to be used by researchers, consultants or project managers in the analysis of collaboration. This analysis can lead to the understanding of collaboration aspects and identification of the problems caused. Consequently, guidelines can be defined to prevent the re-emergence of the identified design problems in new projects. These guidelines are recommendations to introduce collaborative aspects, flexibility in the design process and elements for decision making when defining future design situations. Finally, a study of a specific application implementing PLM tools demonstrates that they are not able to manage firstly design projects and human resources whilst taking into account collaborative aspects or, secondly, the necessary synchronisation between human design activities and document workflow tasks. It is thus evident that these two factors are needed in PLM tools in order to apply the proposed model of coordination. An industrial partnership with an SME led to the study of its information system, an experiment with the CoCa tool, practical design process improvements, and implementation of a PLM prototype.Item Open Access A methodology for the concurrent design of products and their assembly sequence(Cranfield University, 1999) Barnes , C. J.; Jared, GrahamThis thesis reports on the development of a Two-Tier methodology that provides support for assembly sequence construction, validation and evaluation in parallel with the design. This facilitates the production of products that are optimised for assemblability. The proposed approach diverges significantly from many of the sequence generation methods developed to date, which assume that assembly planning starts at the conclusion of the design process. It is believed that the latter approach misses an important opportunity to concurrently implement design and sequence improvements that would result in products inherently suited to assembly. The industrial assembly planning process was found to be completely different from the automatic sequence generation approach. The Two-Tier methodology has its foundations in this manual process, which uses a breadth-first, depth-second search. A constraint-based method is used to interactively validate the sequence. In direct contrast to traditional sequence generators, the hard and soft constraints are invoked throughout the process. A novel approach to sequence evaluation allows the user to quantitatively determine the suitability of the sequence at any time during the construction process. However, designers are rarely assembly experts and it is unreasonable to expect practical sequences to be generated without assistance. Thus, a set of generic assembly planning rules was identified from industrial surveys by the author. These were collaboratively implemented into an Expert Assembler, which currently consists of two mini advisors. Support is available to identify the most suitable base component and the most appropriate component to add next. The Two-Tier methodology has been implemented into a computer-based system called SPADE (Sequence Planning And Design Environment). A four-layer model holds the product data that underpins this implementation. The methodology and SPADE have been successfully tested using representative case studies and the results are reported as part of this thesis.Item Open Access Product complexity assessment for a Proactive-DFA implementation (Simplicity + Simplicity = Complexity)(2004-10) Rodriguez-Toro, Carlos A.; Jared, GrahamThis thesis presents product complexity as a criterion for the optimisation of product design in the light of an Assembly-Oriented Design and Design for Assembly implementation. It takes a holistic approach to the evaluation of the product architecture by presenting a set of indicators that help examine the product structure at two different levels: Assembly and Component complexity. Assembly complexity assessment is further sub-divided into Structural and Sequence complexity. The latter is a well-known and thoroughly studied area in assembly sequence evaluation, whereas the former gives a novel and original approach to drawing attention to those areas in the product configuration that will consume more resources (i.e. time and tooling required). Component complexity, on the other hand, is sub-divided into manufacturing and process handling/manipulation complexity. The first area has been addressed by the manufacturing analysis section of most Design for Assembly and Manufacturing methodologies, but it has been traditionally addressed as a manual and chart-based evaluation. This is a rigid approach that leaves little room for expansion and has no connection with the product structure. The metrics presented in this work embody a new approach that takes into account the component-to-component interactions and allows the analysis of component shape by extracting its geometry characteristics and comparing them with particular traits of the manufacturing processes available to the designer. Additionally, the metrics presented in this work can be used to make an assessment of the product complexity at a particular point (static complexity) in the development cycle. They can also be registered over a period of time to provide an estimate of the possible consequences of the decisions made during a part of the development cycle (dynamic complexity). By using the methods developed, designers could reduce production costs and increase the reliability of their products.